The present invention relates to bearings and more particularly to sealed bearing assemblies and seals therefor.
In certain applications, it is necessary to employ a bearing assembly which will accommodate shaft end play and misalignment. For example, bearings which support conveyor rollers should accommodate center loading of the rollers without undue stress. The bearing assemblies have a certain amount of designed-in internal clearance which avoides preload on the bearing elements and permits accommodation of radial and axial movement. Loose bearing assemblies are also used in trolley wheels of overhead trolley conveyor systems and in assemblies which guide conveyor chain around turns.
Bearing assemblies which accommodate such movement suffer from an inherent disadvantage. Repeated shifting of an inner race with respect to an outer race may produce a pumping action. Grease or other lubricant may be pumped out of the bearing and dirt, dust and the like may, in effect, be pumped in. When such assemblies are used in inherently dusty or dirty environments, such as in agricultural uses or in certain conveyor uses, a need exists to provide a seal which will seal both the inside and the outside of the bearing assembly while accommodating bearing movement.
Heretofore, attempts have been made to provide bearings and bearing seals which will protect the assembly from entry of foreign matter and from loss of lubricant. An example of one such approach may be found in U.S. Pat. No. 3,203,740 entitled BEARING SEAL and issued on Aug. 31, 1965, to Pieckii et al. As disclosed therein, an inner race of a ball bearing assembly is provided with an annular ridge. A sealing member carried by an outer race includes a pair of parallel lips which are deformed and ride one on each of the walls of the ridge structure. The inner lip seals in lubricant and an outer lip excludes dirt, dust and other foreign matter. Due to the construction of the seal, proper functioning requires accurate axial location of the lips of the seal. This is achieved by maintaining tolerances of the bearing structure during manufacture. Therefore, radial and axial movement of the inner race may have an adverse effect on the functioning of the seal.
Examples of other heretofore proposed sealing arrangements may be found in U.S. Pat. No. 2,144,691, entitled BEARING SEAL and issued on Jan. 24, 1939, to Schmal; U.S. Pat. No. 3,595,587, entitled PROTECTIVE SUPPORT FOR BALL BEARINGS and issued on July 27, 1971, to Senigalliesi; and U.S. Pat. No. 3,814,446, entitled SEALING ARRANGEMENT and issued on June 4, 1974, to Derman. Senigalliesi and Derman both disclose seals including flexible membrane portions which will accommodate radial and/or axial deformation of movement of the bearing.
A need exists for an effective and relatively easy to manufacture sealing structure which will readily accommodate radial and axial movement of a loose bearing assembly and which will negate the aformentioned pumping action.